=pod =head1 NAME ECDSA_SIG_get0, ECDSA_SIG_set0, ECDSA_SIG_new, ECDSA_SIG_free, i2d_ECDSA_SIG, d2i_ECDSA_SIG, ECDSA_size, ECDSA_sign, ECDSA_do_sign, ECDSA_verify, ECDSA_do_verify, ECDSA_sign_setup, ECDSA_sign_ex, ECDSA_do_sign_ex - low level elliptic curve digital signature algorithm (ECDSA) functions =head1 SYNOPSIS #include ECDSA_SIG *ECDSA_SIG_new(void); void ECDSA_SIG_free(ECDSA_SIG *sig); void ECDSA_SIG_get0(const ECDSA_SIG *sig, const BIGNUM **pr, const BIGNUM **ps); int ECDSA_SIG_set0(ECDSA_SIG *sig, BIGNUM *r, BIGNUM *s); int i2d_ECDSA_SIG(const ECDSA_SIG *sig, unsigned char **pp); ECDSA_SIG *d2i_ECDSA_SIG(ECDSA_SIG **sig, const unsigned char **pp, long len); int ECDSA_size(const EC_KEY *eckey); int ECDSA_sign(int type, const unsigned char *dgst, int dgstlen, unsigned char *sig, unsigned int *siglen, EC_KEY *eckey); ECDSA_SIG *ECDSA_do_sign(const unsigned char *dgst, int dgst_len, EC_KEY *eckey); int ECDSA_verify(int type, const unsigned char *dgst, int dgstlen, const unsigned char *sig, int siglen, EC_KEY *eckey); int ECDSA_do_verify(const unsigned char *dgst, int dgst_len, const ECDSA_SIG *sig, EC_KEY* eckey); ECDSA_SIG *ECDSA_do_sign_ex(const unsigned char *dgst, int dgstlen, const BIGNUM *kinv, const BIGNUM *rp, EC_KEY *eckey); int ECDSA_sign_setup(EC_KEY *eckey, BN_CTX *ctx, BIGNUM **kinv, BIGNUM **rp); int ECDSA_sign_ex(int type, const unsigned char *dgst, int dgstlen, unsigned char *sig, unsigned int *siglen, const BIGNUM *kinv, const BIGNUM *rp, EC_KEY *eckey); =head1 DESCRIPTION Note: these functions provide a low level interface to ECDSA. Most applications should use the higher level B interface such as L or L instead. B is an opaque structure consisting of two BIGNUMs for the B and B value of an ECDSA signature (see X9.62 or FIPS 186-2). ECDSA_SIG_new() allocates an empty B structure. Note: before OpenSSL 1.1.0 the: the B and B components were initialised. ECDSA_SIG_free() frees the B structure B. ECDSA_SIG_get0() returns internal pointers the B and B values contained in B. The B and B values can be set by calling ECDSA_SIG_set0() and passing the new values for B and B as parameters to the function. Calling this function transfers the memory management of the values to the ECDSA_SIG object, and therefore the values that have been passed in should not be freed directly after this function has been called. i2d_ECDSA_SIG() creates the DER encoding of the ECDSA signature B and writes the encoded signature to B<*pp> (note: if B is NULL i2d_ECDSA_SIG() returns the expected length in bytes of the DER encoded signature). i2d_ECDSA_SIG() returns the length of the DER encoded signature (or 0 on error). d2i_ECDSA_SIG() decodes a DER encoded ECDSA signature and returns the decoded signature in a newly allocated B structure. B<*sig> points to the buffer containing the DER encoded signature of size B. ECDSA_size() returns the maximum length of a DER encoded ECDSA signature created with the private EC key B. ECDSA_sign() computes a digital signature of the B bytes hash value B using the private EC key B. The DER encoded signatures is stored in B and its length is returned in B. Note: B must point to ECDSA_size(eckey) bytes of memory. The parameter B is currently ignored. ECDSA_sign() is wrapper function for ECDSA_sign_ex() with B and B set to NULL. ECDSA_do_sign() is similar to ECDSA_sign() except the signature is returned as a newly allocated B structure (or NULL on error). ECDSA_do_sign() is a wrapper function for ECDSA_do_sign_ex() with B and B set to NULL. ECDSA_verify() verifies that the signature in B of size B is a valid ECDSA signature of the hash value B of size B using the public key B. The parameter B is ignored. ECDSA_do_verify() is similar to ECDSA_verify() except the signature is presented in the form of a pointer to an B structure. The remaining functions utilise the internal B and B values used during signature computation. Most applications will never need to call these and some external ECDSA ENGINE implementations may not support them at all if either B or B is not B. ECDSA_sign_setup() may be used to precompute parts of the signing operation. B is the private EC key and B is a pointer to B structure (or NULL). The precomputed values or returned in B and B and can be used in a later call to ECDSA_sign_ex() or ECDSA_do_sign_ex(). ECDSA_sign_ex() computes a digital signature of the B bytes hash value B using the private EC key B and the optional pre-computed values B and B. The DER encoded signature is stored in B and its length is returned in B. Note: B must point to ECDSA_size(eckey) bytes of memory. The parameter B is ignored. ECDSA_do_sign_ex() is similar to ECDSA_sign_ex() except the signature is returned as a newly allocated B structure (or NULL on error). =head1 RETURN VALUES ECDSA_SIG_set0() returns 1 on success or 0 on failure. ECDSA_size() returns the maximum length signature or 0 on error. ECDSA_sign(), ECDSA_sign_ex() and ECDSA_sign_setup() return 1 if successful or 0 on error. ECDSA_do_sign() and ECDSA_do_sign_ex() return a pointer to an allocated B structure or NULL on error. ECDSA_verify() and ECDSA_do_verify() return 1 for a valid signature, 0 for an invalid signature and -1 on error. The error codes can be obtained by L. =head1 EXAMPLES Creating an ECDSA signature of a given SHA-256 hash value using the named curve prime256v1 (aka P-256). First step: create an EC_KEY object (note: this part is B ECDSA specific) int ret; ECDSA_SIG *sig; EC_KEY *eckey; eckey = EC_KEY_new_by_curve_name(NID_X9_62_prime256v1); if (eckey == NULL) { /* error */ } if (EC_KEY_generate_key(eckey) == 0) { /* error */ } Second step: compute the ECDSA signature of a SHA-256 hash value using ECDSA_do_sign(): sig = ECDSA_do_sign(digest, 32, eckey); if (sig == NULL) { /* error */ } or using ECDSA_sign(): unsigned char *buffer, *pp; int buf_len; buf_len = ECDSA_size(eckey); buffer = OPENSSL_malloc(buf_len); pp = buffer; if (ECDSA_sign(0, dgst, dgstlen, pp, &buf_len, eckey) == 0) { /* error */ } Third step: verify the created ECDSA signature using ECDSA_do_verify(): ret = ECDSA_do_verify(digest, 32, sig, eckey); or using ECDSA_verify(): ret = ECDSA_verify(0, digest, 32, buffer, buf_len, eckey); and finally evaluate the return value: if (ret == 1) { /* signature ok */ } else if (ret == 0) { /* incorrect signature */ } else { /* error */ } =head1 CONFORMING TO ANSI X9.62, US Federal Information Processing Standard FIPS 186-2 (Digital Signature Standard, DSS) =head1 SEE ALSO L, L, L =head1 COPYRIGHT Copyright 2004-2016 The OpenSSL Project Authors. All Rights Reserved. Licensed under the OpenSSL license (the "License"). You may not use this file except in compliance with the License. You can obtain a copy in the file LICENSE in the source distribution or at L. =cut